The present invention relates to electrophotographic copying machines, such as electrophotographic duplicators, electrophotographic plate making machines of electro-fax type plate making machines, or the like.
Conventional electrophotographic copying machines involve various problems which should be solved. One of the problems relates to a "black frame", as mentioned in the specification of U.S. Pat. No. 3,901,593. As is well known in the art, when a partial area of a photosensitive paper is exposed to the light of an original or manuscript, a black frame is formed at the remaining area not exposed, that is around the exposed area.
To cope with the above mentioned problem the following methods have been adopted.
A photosensitive paper, the surface of which is smaller than an exposed area, has been used or an exposed area has been designed so as to be larger than the surface of a photosensitive paper, thus preventing the formation of the black frame. Alternatively, eraser light sources have been used for illuminating undesirable images formed on selected marginal areas of the photosensitive paper for the purpose of preventing the formation of the undesirable black frame on the marginal areas. Copying apparatus provided with such eraser light sources are disclosed in U.S. Pat. No. 3,724,940 and U.S. Pat. No. 3,901,593.
In the conventional copying machine of a wet type, a process for squeezing a developing liquid from a developed paper, subsequent to a wet developing process, involves the following problem. In the squeezing process there is generally used a squeezing roller assembly comprising a pair of rollers urged by spring means so as to press the developed paper passing between the rollers. The surplus developing liquid is thus squeezed from the paper so that fixing and drying of the developed paper are promoted. However, such rollers always have the developing liquid adhered on their surfaces. As a result, when the rollers are operated for a long time, solid layers of the developing liquid are fixed on the surfaces of rollers. This causes a reduction in the squeezing efficiency with the result that the quality of the developed image on the paper is reduced. Further, while the copying operation of the machine is stopped, the developing liquid adhered to the squeezing rollers is vaporized with the result that a toner included in the liquid only remains on the surface of the rollers. In such a situation, if the copying operation is resumed, the residual toner is transferred onto the surface of a developed paper. This causes contamination of the developed image surface of the paper. For this reason, it is necessary to wash and clean the rollers so that the adhered toner is removed from the rollers after the rollers are used for a predetermined operation period. For the washing and cleaning, the means for urging the rollers, such a spring, must be released and, then, a roller positioning and holding means must be removed, so that the rollers can be removed from the machine. Such releasing and removing operations are, in general, carried out from the front side and rear sides of the machine housing, respectively. Further, after the washing and cleaning, the cleaned rollers must be mounted in the machine at predetermined positions in accordance with operations which are the reverse of the above mentioned operations. Such removing and mounting operations are troublesome for operators. However, it is noted that, the above troublesome operations are tolerable in a copying machine of a small scale, but are not tolerable in a large copying machine of console type or the like. With respect to such large machines, because of such maintainance operations, the machines can not be installed near the wall of a room and, thus, a floor space larger than the space occupied by the machine is required for the installation of the machine.
In general, a copying machine has a relatively complicated optical system for exposing a photosensitive paper to a light image of an original. Because of this system the machine housing must be of a large scale so that the optical system can be accomodated in the housing. For example, a conventional optical system comprises a reflective mirror and a projection lens in an arrangement such that a light image formed by the light on an original mounted on an original supporting window is, first, reflected by the mirror and, then, passes through the lens to be focused on a photosensitive paper. Such optical system naturally requires a long path of the light image along the optical axis of the lens to focus the image on the paper and, thus, requires a machine housing of large scale.
There are two kinds of copying machines, one of which is provided with a magazine for supporting a plurality of laminated photosensitive papers, which are supplied, one by one, from the magazine and are subjected to deposition of an electrostatic charge, and then, to exposure to a light image of an original, and the other of which is provided with a roll of photosensitive paper which is cut to the required size by a cutting means to provide a separate paper, which is subsequently subjected to deposition of an electrostatic charge and, then, to exposure to a light image of an original.
The copying machine, in which the roll of photosensitive paper is used, involves a serious problem in that, since the forward portion of the roll paper is cut to the required size while being conveyed toward an electrostatic charger, the cut edge of the paper must be inclined to a direction perpendicular to the paper over the width thereof. In a case where the paper separated from the roll with the inclined cut edge is processed by a copying machine, particularly by a plate making machine, to form a master and the master is used as an original in an automatic printing machine, the inclined cut edge of the master causes not only an unstable gripping of the master for positioning the master, but also, causes production of printed papers wherein the printed images are displaced from predetermined positions. To avoid the above disadvantages, the copying machine must cut the forward portion of a roller paper while the portion is conveyed at a very low speed.
According to the methods for avoiding the above mentioned disadvantages, which are disclosed in the Japanese Utility Model application of Publication No. 992/50 and the Japanese Patent application of Publication No. 27141/51, two pairs of rollers are provided upstream and downstream of the cutting means in the copying machine to cause a slack in a portion of the paper between the two pairs of rollers. The cutting means is actuated to cut the paper at the slack portion thereof. However, such a cutting method has a disadvantage that the cutting means is apt to contact the surface of the slack portion just before cutting, thereby causing scratches and/or partial cuts in the paper which will be copied on papers in the printing machine.
To solve the above disadvantageous problem, there is proposed in Japanese Patent application Disclosure No. 61237/50 a method wherein a first pair of rollers with a one way clutch are provided upstream of the cutting means, while a second pair of rollers with a one way clutch are provided downstream of the cutting means and a third pair of rollers without any one way clutch are provided downstream of the second rollers. After a roll of paper is made slack between the second and third pairs of rollers, the rotations of the first and second pairs of rollers are stopped, and then, the cutting means is actuated to cut the portion of the paper between the first and second pairs of rollers.
According to the above mentioned method, when the first and second pairs of rollers stop, a portion of the paper between the first and second pairs of rollers becomes stationary and tensioned. However, while the cutting means is acting against the tensioned paper portion to be cut between the first and second pairs of rollers, the tension of that paper portion is released so that paper portion is made slack. This is because the one way clutch connected to the first pair of rollers permits the first pair of rollers to rotate so that the paper portion to be cut is fed out of the first pair of rollers when that paper portion is drawn in the downstream direction. That is, the paper portion between the first and second pairs of rollers is cut by the cutting means while that paper portion is caused to be slack by the one way clutch connected to the first pairs of rollers. Therefore, the cutting means can not exhibit its function adequetely. Further, while the cutting means is returning upwardly to a normal position, it is apt to bend the forward portion of the roll paper upwardly with the cut edge. This results in a danger of the paper being jammed in the subsequent processes.
Further, in a case where a roll of paper is to be replaced with a new one of another size, it is difficult to carry out the replacement. This is because the first pair of rollers are not allowed to rotate in such a direction that the forward portion of the paper is caused to move back in the upstream direction through the first pair of rollers. Therefore it is difficult to remove the roll of paper, the forward portion of which is nipped by the first pair of rollers, from the first pair of rollers. If the roll of paper is forcibly removed from the first pair of rollers, the surface of the forward portion of the roll of paper is damaged by scratches due to friction against the rollers.
In the conventional copying machine, a paper cutting device comprises means for setting a length of the paper to be cut to a required value, which means is of a relatively complicated construction. In this respect, it is desirable to provide a length setting means of a simple construction whereby accurate cutting of paper to the required length is ensured.
A copying machine is provided with an original supporting window of glass plate and an original depressing plate means thereon. The original is sandwitched between the supporting window and the depressing plate means.
A well known original depressing plate means consists of a rectangular covering plate of rubber or the like having a substantial weight. The covering plate is pivoted to the original supporting window at one end, while the other free end of the plate has a grip means. The covering plate serves as a weight for depressing the original against the original supporting window. In a case where an original of a large thickness such as a book is placed on the supporting window, the covering plate is required to have weight enough to depress the original in a substantially flat manner. Otherwise, a portion of the original will be spaced apart from the surface of the window and, thus, the light image will be out of focus or the copied image will be distorted. However, a covering plate of an increased weight is a burden to an operator handling the plate, and obstructs the swift operation of the covering plate. Therefore, it is realized that the conventional covering plate means has two contradictory requirements as mentioned above.
Further, the conventional covering plate involves the following problem. The covering plate falls down backwardly when it is turned over from the window. In such case, the operator is required to take an abnormal pose for putting the plate back onto the window. Particularly, in a case where the window is positioned at a high level relative to the floor, the operator is compelled to handle the covering plate in such manner that he stretches himself from the floor.
A copying machine such as an electrophotographic duplicator or an electrophotographic plate making machine is provided with a paper conveying assembly by which papers processed in the copying machine are conveyed successively out of the machine for subsequent process. There are cases where such papers are required to be conveyed from a lower level to a higher level as a matter of convenience for a subsequent process or a manual operation. For example, in a copying machine of a console type, such as a duplicator or a plate making machine, an outlet for the processed papers is provided at a position located at a relatively high level. This is because, with such copying machine, it is required to be easy to take out the processed papers and a printer, in which the processed papers are to be used as a master plate for printing, is provided with a plate positioning station at a position located at a relatively high level. With such copying machine, it is usual to carry out a developing process and a subsequent fixing process in the lower zone of the machine housing. In order to carry out the fixing process, there has been proposed a belt conveyor provided with a suction box disposed therein so as to adhere a paper on the belt surface by means of suction pressure and with a chain delivery assembly having means for chucking the forward end of the paper to be conveyed. However, with such a conveyer, an expensive closed box with a fan or blower is required. This causes the conveyor to be of a relatively complicated construction. The conveyor of such complicated construction has a tendency to become out of order while it is used. Therefore, the conveyor requires troublesome operations for its maintenance in order to use it for a long time.
With the above mentioned chain delivery assembly, it is necessary to incorporate means for detecting the forward end of the paper in the assembly, so that the chucking means can chuck the forward end of the paper. Therefore, the chain delivery assembly becomes expensive.